This application relates to systems for stabilizing electric power steering systems, such as in the automotive arts.
Steering equipment for assisting a driver to steer an automobile is well known in the art. In conventional steering assemblies, the operator controls the direction of the vehicle with the aid of a steering wheel mechanically connected, usually through a gear assembly to the road wheels. To aid the operator, many systems utilize an auxiliary system to generate a force that is transmitted to a steering gear assembly. The additional force reduces the effort required by the operator in changing the direction of the vehicle. Typically, this auxiliary force is generated by either a hydraulic drive or an electric motor.
Because the steering wheel is connected directly to the road wheels, the resulting mechanical assembly that provides the connection can be quite complicated and expensive to produce. The one advantage in having a direct connection is that the operator receives tactile feedback through the steering wheel. For example, if the vehicle changes directions while it is moving, the operator will feel resistance in the steering wheel.
It is known in the art of electric power steering systems to vary the amount of assist, or commanded torque, as a function of vehicle speed, handwheel position, and handwheel torque. However, the previous systems may be inadequate under certain adverse road conditions, such as wet or icy roads.
Therefore, is it considered advantageous to provide an electric steering control system that provides desirable assist torque and tactile feedback to the operator and yet maintains system stability under adverse road conditions.
A method of stabilizing a vehicle employing an electric power steering system is disclosed. In addition, a system, which implements the method is also disclosed. The method includes receiving as inputs, a desired torque command representative of a steering wheel torque desired in the electric power steering system and a vehicle speed signal representative of a forward speed of the vehicle. The method also includes acquiring an acceleration signal representative of the vehicle acceleration measured by an acceleration sensor.
The method further comprises generating an assist torque command, which is a combination of the desired torque command and a compensating torque command where the compensating torque command is responsive to the vehicle speed signal and the acceleration signal. The assist torque command is transmitted to an assist mechanism for application of an assist torque to the vehicle steering system.
The above-described and other features and advantages will be appreciated and understood by those skilled in the art from the following detailed description, drawings, and appended claims.